(350d) Modelling, Simulation and Experimental Investigation of Hybrid Separation Processes

Reactive separations such as reactive distillation which are combining reaction and separation in one apparatus have been established in process technology. The combination of reactive separations with other separation operations can lead to a more sustainable and economic process performance due to strong synergy effects and hence, is at present a focus of academic and industrial research. A promising example seems to be the combination of a reactive distillation column with membrane separation to a hybrid reactive separation process, since the membrane separation is selective and independent of the vapour-liquid equilibrium. In this work, the heterogeneously catalysed esterification of propionic acid with 1-propanol to n-propylpropionat and water in a membrane assisted reactive distillation column is investigated. Such a hybrid process combines the specific benefits of each unit-operation: it shows higher conversions compared to the corresponding chemical equilibrium because of selective product removal from the reactive part of the column and simultaneous dewatering of the produced non-ideal aqueous-organic mixtures. Since the operation of a plant consisting of coupled reactive distillation and membrane separation is very complex, at first the independently operated units are experimentally investigated in order to prove their applicability. Reactive distillation experiments are performed within a pilot plant RD-column (DN50) equipped with Sulzer BX and Katapak-SP 11 elements. The total packing height is 5.5m. The experimental results show the influence of decisive operational parameters and column loadings on concentration and temperature profiles. Binary water/alcohol and ternary alcohol/ester/water vapour permeation experiments are performed in a multifunctional lab-scale plant equipped with a flat membrane test cell from Sulzer Chemtech to determine the separation characteristics of the used polymeric membrane Pervap 2201D. To analyse scale-up effects on the efficiency of technical membrane modules, results of pilot-scale experiments with a membrane area of 0.5 m² are shown. Finally, the pilot-scale reactive distillation column connected with the vapour permeation unit have been experimentally investigated. The aim of the experiments is on the one hand to demonstrate the advantages of the advanced process concept and on the other hand to provide reliable data for the validation of detailed rate-based models for both reactive distillation and membrane separation. The validated process model allows investigating the influence of structural and operational parameters of the hybrid process on conversion and required heat duty and exhibit the basis for a rigorous process optimisation.